1. Field of the Invention
This invention relates to a thin film magnetic head device for a hard disk, which is of a structure such that a thin film magnetic head is directly formed on a slider member comprised of a rigid substrate or base to carry out recording onto a hard disk and reproducing therefrom.
2. Description of the Prior Art
A magnetic head device for writing an information signal onto the so-called hard disk or reading it out therefrom is caused to be typically of the flying type in which a slider flies with a very small spacing from the disk surface in recording/reproduction. Accordingly, the slider and the magnetic head are ordinarily of an integral structure.
Heretofore, as the magnetic head device of this kind, there is known a magnetic head device of the monolithic type in which the entirety thereof including, e.g., a slider, is integrally formed by a ferrite material, and so forth, a magnetic head device of the composite type in which a magnetic head separately made up is buried into a slider, and a magnetic head device of the thin film type in which a thin film magnetic head is directly formed on a slider by the vacuum thin film formation technology.
Especially, in the magnetic head device of the thin film type, a metal magnetic film having a high saturation magnetic flux density is used as a magnetic core. Therefore, such a magnetic head device has excellent merit in that the magnetic field distribution is steep or sharp, the inductance is small, and so forth. Accordingly, under the circumstances where an improved recording density and/or a high speed transfer rate are required, it is exceedingly expected that such magnetic head devices of the thin film type are put into practice.
However, in the above-mentioned magnetic head device of the thin film type, there takes place a problem peculiar to the thin film magnetic head, which is so called a core recess, due to the fact that the slider and the magnetic core of the thin film magnetic head are greatly different from each other in material.
The above-mentioned core recess is formed after processing of an opposite surface to a hard disk (air bearing surface), and is the phenomenon that the magnetic core of the thin film magnetic head is withdrawn from the air bearing surface.
For example, in the case where the slider is comprised of a very hard material such as Al.sub.2 O.sub.3 --TiC, and so forth, since the magnetic core of the thin film magnetic head is comprised of a relatively soft metal magnetic film, polishing of only this metal magnetic film is selectively developed, so a magnetic gap for carrying out recording/reproduction is somewhat withdrawn from the air bearing surface.
As stated above, when a core recess takes place so that the magnetic gap is withdrawn from the air bearing surface, the spacing between the hard disk and the magnetic head becomes greater, thus making it difficult to attain a high recording density.
Various methods have been proposed as a measure for minimizing the core recess. With these methods, improvements can be made to some degree. For example, if a very fine abrasive or polishing material is used to carry out polishing for a long time, such core recess might be reduced.
However, the manufacturing cost extremely increases with reduction of a recess quantity. Therefore, this method is not so effective in practical use.